(1) Field of the Invention
This invention relates to conveyor belts and, more particularly, to food processing belts and other conveyances molded of conductive loaded resin-based materials comprising micron conductive powders, micron conductive fibers, or a combination thereof, homogenized within a base resin when molded.
(2) Description of the Prior Art
Conveyors, chutes, skids, guides, and ways for the transporting of material and articles of manufacturing are well known in the art. In the food processing industry, conveyors are used for warming and cooling food products, slicing and bagging, in-feed and discharge. The conveyor belts are generally constructed of a plastic resin such as Polypropylene, Polyethylene, Acetal, or the like, or may be constructed of a metal wire frame with an over-molded plastic resin. The conveyor belts allow processed material to be transported while remaining level and flat. Conveyors, chutes, skids, guides, and ways may be fabricated to be electrically conductive to dissipate static electricity, may be heat resistant for use in high temperature processing of food, may be moisture tolerant for wet environments, may be impact resistant to prevent breakage of glass food packaging, and may be flame retardant to prevent sustaining a flame.
A problem that may occur with plastic resin belts or with metal wire frame belts that are covered in plastic resin is wear-out induced contamination. As the plastic resin material wears out, particulate material from the plastic resin may brake away from the belt. As a result, it is possible for this material to contaminate a food item being processed on the belt. This contamination is undesirable both in terms of food safety and of consumer acceptance.
Several prior art inventions relate to Conveyors, chutes, skids, guides, and ways and to items comprising conductive plastics. U.S. Pat. No. 6,368,704 to Murata, et al provides a conductive paste that exhibits a high thermal conductivity (a low thermal resistance) after adhesion and hardening that enables an adhesive layer to be thinly formed and provides an electronic part that has an excellent radiating capability that enables the film's thickness to be reduced. U.S. Pat. No. 6,277,303 to Foulger describes conductive polymer composite materials. The conductive polymer composite material includes a minor phase material that has a semicrystalline polymer. The composite material further includes a conductive filler material dispersed in the minor phase material in an amount sufficient to be equal to or greater than an amount required to generate a continuous conductive network within the minor phase material. U.S. Pat. No. 4,197,218 to McKaveney describes electrically conductive articles. The articles are formed of a non-conductive matrix containing an electrically conductive dispersion of finely divided ferroalloy, silicon alloy, or mixtures. U. S. Pat. No. 6,602,446 to Ushijima provides an electrically conductive paste made up of an electrically conductive filler and a conveyor belt adapted to generate heat by electromagnetic induction are compounded with a resin.
INTRALOX Inc. USA, 201 Laitram Lane, Harahan, La. 70123, Ammeraal Beltech, 75011 N. St. Louis Ave., Skokie, Ill. 60076, and Siegling America, Inc., 12201 Vanstory Road, Huntersville, N.C. 28078 are manufacturers of conveyor belting. Each manufacturer describes conductive belting manufactured of plastic resins with embedded conductors. Cassel Messtechnik GmbH, Carl-Giesecke-Str. 3, 37079 Göttingen, Germany manufactures a metal detector for the food industry. The metal detector operates on the basis of an inductive measuring principle. A high-frequency electromagnetic alternating field is generated by a transmitter coil. If a metal piece passes through the metal detector, the field experiences a change corresponding to the magnetic and electrical properties of the metal piece. In the article by McCluskey, et al., “Nanocomposite Materials Offer Higher Conductivity and Flexibility”, Proceedings of 3rd International Conference on Adhesive Joining and Coating Technology in Electronics Manufacturing, 1998, pp: 282–286, the mechanical and electrical characteristics of a conductive polymer made with conductive silver flake nanoparticle fillers is described. In the article by Fan et al., “Fundamental Understanding of Conductivity Establishment for Electrically Conductive Adhesives,” Proceedings of the 52nd Electronic Components and Technology Conference, 2002, pp: 1154–1157, several epoxy resin based curing systems are described.